1. Field of the Invention
The present invention relates generally to an array of optical waveguides and/or laser diodes in a semiconductor body.
2. Description of the Related Art
Laser diodes, also known as semiconductor lasers, are known. A laser diode can be used to emit a high intensity, highly focused laser emission. However, the light power per area of the laser diode emission is limited, particularly when additional requirements are made of the generated laser emission. One such requirement, resulting in the limitation of the output power for a laser diode, is when the emission is required to be, for example, a monomode emission.
It is possible to achieve higher light powers when a plurality of identical laser diodes are operated in parallel with their laser emissions geometrically optically combined. For instance, parallel operation is known in laser diode arrays. When laser diode arrays are used specifically for communication transmissions, it is important that all of the individual laser diodes meet the aforementioned requirement and emit the laser emission at the same frequency and in the same emission mode, and preferably of a uniform phase.
It has long been known to provide a plurality of laser diodes each having a laser-active strip integrated into a single semiconductor body or monolith. The individual strips of the laser diodes are disposed in close proximity and parallel to one another. It is also known to achieve the monomode emission and phase identity of the laser signal emitted from adjacent diode strips by arranging the laser diode strips close enough to one another that lateral coupling occurs between the individual laser beams. In other words, the laser emissions of respective neighboring laser strips are waveoptical coupled.
It is desired to have laser diodes with a threshold current for laser-active operation, that is, as low as possible. Low threshold currents are achieved when there is good lateral wave-guidance of the laser emission generated within the strip structure of the laser diode. Good lateral wave-guidance, and low threshold currents, are present in index-guided laser diodes as disclosed in U.S. Pat. No. 4,352,187 and as described in the publication "Frequenz", vol. 34 (1980) pages 343-346.
The desirable low threshold current, however, opposes an efficient coupling of neighboring laser strips, since the active regions of respective laser diode strips projects only slightly laterally beyond the actual strip region. In other words, the overlap of the active regions of adjacent laser diode strips is only small and, therefore, not very effective. To nevertheless achieve an adequate optical coupling, a very small spacing between neighboring laser diode strips is required. Since this, however, brings rise to substantial technical difficulties, it is preferred to use an oxide strip laser operating on the principle of a gain-guided laser which has significantly weaker lateral wave-guidance so as to guarantee good coupling between neighboring strips.